This invention relates to a telephone circuit echo canceller of the type employing a digital transversal filter which adapts to cancel the echo.
A telephone circuit echo canceller using an adaptive filter can effectively cancel the echo introduced by a hybrid. In doing so, the filter adapts to include the impulse response of the echo producing system. This includes any transmission delay from the canceller to the hybrid and back, during which period the impulse response is approximately zero. If transversal filter delays and coefficients are provided to incorporate the entire impulse response, a very large portion of the filter is occupied, inefficiently, with providing nothing more than a fixed delay.